Musar על עבודה זרה 36:13

And now we shall speak about the faculty of hearing. Hearing, in itself, is good, as it is written (Isaiah 55:3): "Hear, and let your souls live." And (Mishlei 15:31): "The ear that hears the reproof of life, in the midst of the wise will it reside." And hearing works on a man to cause him to satisfy [an obligation] by hearing as if he had performed it himself. A proof may be adduced from the reading of the Megillah, the blowing of the shofar, and other such things, such as [the recitation of] Kiddush and the grace over meals, where one makes the blessing and all the listeners satisfy the obligation. Similarly, all of the receiving of the Torah was through hearing. All this, for good things. The reverse is true for bad things, G-d forbid. Hearing [bad things] also greatly affects a man's soul. It is well known what our sages of blessed memory have said (Kethuvoth 5b): "The Rabbis taught: 'Let a man not allow idle speech to be heard by his ears, for they are the first of the organs to be "burnt."'" How much more so [does this apply] to one who intends to cause rechiluth to be heard by his ears, this being proscribed by a negative commandment in the Torah, viz. (Shemoth 23:1): "You shall not bear a false report," or to one who hears, with intent, lashon hara and other forbidden things, or frivolous speech or leitzanuth (levity), in which instance his sin is too great to bear. And our sages of blessed memory have said about the scoffer (Avodah Zarah 18b) that suffering comes upon him, as it is written (Isaiah 28:22): "Do not scoff, lest your bonds be strengthened." And they have also said (Shabbath 33a): "Even he who listens [to obscenity] and remains silent [is condemned], it being written (Mishlei 22:14): 'The abhorred of the L-rd will abide there' [next to the speaker of obscenity.]"